// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/compilation-cache.h"

#include "src/counters.h"
#include "src/globals.h"
#include "src/heap/factory.h"
#include "src/log.h"
#include "src/objects-inl.h"
#include "src/objects/compilation-cache-inl.h"
#include "src/objects/slots.h"
#include "src/visitors.h"

namespace v8 {
namespace internal {

    // The number of generations for each sub cache.
    static const int kRegExpGenerations = 2;

    // Initial size of each compilation cache table allocated.
    static const int kInitialCacheSize = 64;

    CompilationCache::CompilationCache(Isolate* isolate)
        : isolate_(isolate)
        , script_(isolate)
        , eval_global_(isolate)
        , eval_contextual_(isolate)
        , reg_exp_(isolate, kRegExpGenerations)
        , enabled_(true)
    {
        CompilationSubCache* subcaches[kSubCacheCount] = { &script_, &eval_global_, &eval_contextual_, &reg_exp_ };
        for (int i = 0; i < kSubCacheCount; ++i) {
            subcaches_[i] = subcaches[i];
        }
    }

    Handle<CompilationCacheTable> CompilationSubCache::GetTable(int generation)
    {
        DCHECK(generation < generations_);
        Handle<CompilationCacheTable> result;
        if (tables_[generation]->IsUndefined(isolate())) {
            result = CompilationCacheTable::New(isolate(), kInitialCacheSize);
            tables_[generation] = *result;
        } else {
            CompilationCacheTable table = CompilationCacheTable::cast(tables_[generation]);
            result = Handle<CompilationCacheTable>(table, isolate());
        }
        return result;
    }

    void CompilationSubCache::Age()
    {
        // Don't directly age single-generation caches.
        if (generations_ == 1) {
            if (!tables_[0]->IsUndefined(isolate())) {
                CompilationCacheTable::cast(tables_[0])->Age();
            }
            return;
        }

        // Age the generations implicitly killing off the oldest.
        for (int i = generations_ - 1; i > 0; i--) {
            tables_[i] = tables_[i - 1];
        }

        // Set the first generation as unborn.
        tables_[0] = ReadOnlyRoots(isolate()).undefined_value();
    }

    void CompilationSubCache::Iterate(RootVisitor* v)
    {
        v->VisitRootPointers(Root::kCompilationCache, nullptr,
            FullObjectSlot(&tables_[0]),
            FullObjectSlot(&tables_[generations_]));
    }

    void CompilationSubCache::Clear()
    {
        MemsetPointer(reinterpret_cast<Address*>(tables_),
            ReadOnlyRoots(isolate()).undefined_value()->ptr(),
            generations_);
    }

    void CompilationSubCache::Remove(Handle<SharedFunctionInfo> function_info)
    {
        // Probe the script generation tables. Make sure not to leak handles
        // into the caller's handle scope.
        {
            HandleScope scope(isolate());
            for (int generation = 0; generation < generations(); generation++) {
                Handle<CompilationCacheTable> table = GetTable(generation);
                table->Remove(*function_info);
            }
        }
    }

    CompilationCacheScript::CompilationCacheScript(Isolate* isolate)
        : CompilationSubCache(isolate, 1)
    {
    }

    // We only re-use a cached function for some script source code if the
    // script originates from the same place. This is to avoid issues
    // when reporting errors, etc.
    bool CompilationCacheScript::HasOrigin(Handle<SharedFunctionInfo> function_info,
        MaybeHandle<Object> maybe_name,
        int line_offset, int column_offset,
        ScriptOriginOptions resource_options)
    {
        Handle<Script> script = Handle<Script>(Script::cast(function_info->script()), isolate());
        // If the script name isn't set, the boilerplate script should have
        // an undefined name to have the same origin.
        Handle<Object> name;
        if (!maybe_name.ToHandle(&name)) {
            return script->name()->IsUndefined(isolate());
        }
        // Do the fast bailout checks first.
        if (line_offset != script->line_offset())
            return false;
        if (column_offset != script->column_offset())
            return false;
        // Check that both names are strings. If not, no match.
        if (!name->IsString() || !script->name()->IsString())
            return false;
        // Are the origin_options same?
        if (resource_options.Flags() != script->origin_options().Flags())
            return false;
        // Compare the two name strings for equality.
        return String::Equals(
            isolate(), Handle<String>::cast(name),
            Handle<String>(String::cast(script->name()), isolate()));
    }

    // TODO(245): Need to allow identical code from different contexts to
    // be cached in the same script generation. Currently the first use
    // will be cached, but subsequent code from different source / line
    // won't.
    MaybeHandle<SharedFunctionInfo> CompilationCacheScript::Lookup(
        Handle<String> source, MaybeHandle<Object> name, int line_offset,
        int column_offset, ScriptOriginOptions resource_options,
        Handle<Context> native_context, LanguageMode language_mode)
    {
        MaybeHandle<SharedFunctionInfo> result;

        // Probe the script generation tables. Make sure not to leak handles
        // into the caller's handle scope.
        {
            HandleScope scope(isolate());
            const int generation = 0;
            DCHECK_EQ(generations(), 1);
            Handle<CompilationCacheTable> table = GetTable(generation);
            MaybeHandle<SharedFunctionInfo> probe = CompilationCacheTable::LookupScript(
                table, source, native_context, language_mode);
            Handle<SharedFunctionInfo> function_info;
            if (probe.ToHandle(&function_info)) {
                // Break when we've found a suitable shared function info that
                // matches the origin.
                if (HasOrigin(function_info, name, line_offset, column_offset,
                        resource_options)) {
                    result = scope.CloseAndEscape(function_info);
                }
            }
        }

        // Once outside the manacles of the handle scope, we need to recheck
        // to see if we actually found a cached script. If so, we return a
        // handle created in the caller's handle scope.
        Handle<SharedFunctionInfo> function_info;
        if (result.ToHandle(&function_info)) {
#ifdef DEBUG
            // Since HasOrigin can allocate, we need to protect the SharedFunctionInfo
            // with handles during the call.
            DCHECK(HasOrigin(function_info, name, line_offset, column_offset,
                resource_options));
#endif
            isolate()->counters()->compilation_cache_hits()->Increment();
            LOG(isolate(), CompilationCacheEvent("hit", "script", *function_info));
        } else {
            isolate()->counters()->compilation_cache_misses()->Increment();
        }
        return result;
    }

    void CompilationCacheScript::Put(Handle<String> source,
        Handle<Context> native_context,
        LanguageMode language_mode,
        Handle<SharedFunctionInfo> function_info)
    {
        HandleScope scope(isolate());
        Handle<CompilationCacheTable> table = GetFirstTable();
        SetFirstTable(CompilationCacheTable::PutScript(table, source, native_context,
            language_mode, function_info));
    }

    InfoCellPair CompilationCacheEval::Lookup(Handle<String> source,
        Handle<SharedFunctionInfo> outer_info,
        Handle<Context> native_context,
        LanguageMode language_mode,
        int position)
    {
        HandleScope scope(isolate());
        // Make sure not to leak the table into the surrounding handle
        // scope. Otherwise, we risk keeping old tables around even after
        // having cleared the cache.
        InfoCellPair result;
        const int generation = 0;
        DCHECK_EQ(generations(), 1);
        Handle<CompilationCacheTable> table = GetTable(generation);
        result = CompilationCacheTable::LookupEval(
            table, source, outer_info, native_context, language_mode, position);
        if (result.has_shared()) {
            isolate()->counters()->compilation_cache_hits()->Increment();
        } else {
            isolate()->counters()->compilation_cache_misses()->Increment();
        }
        return result;
    }

    void CompilationCacheEval::Put(Handle<String> source,
        Handle<SharedFunctionInfo> outer_info,
        Handle<SharedFunctionInfo> function_info,
        Handle<Context> native_context,
        Handle<FeedbackCell> feedback_cell,
        int position)
    {
        HandleScope scope(isolate());
        Handle<CompilationCacheTable> table = GetFirstTable();
        table = CompilationCacheTable::PutEval(table, source, outer_info, function_info,
            native_context, feedback_cell, position);
        SetFirstTable(table);
    }

    MaybeHandle<FixedArray> CompilationCacheRegExp::Lookup(
        Handle<String> source,
        JSRegExp::Flags flags)
    {
        HandleScope scope(isolate());
        // Make sure not to leak the table into the surrounding handle
        // scope. Otherwise, we risk keeping old tables around even after
        // having cleared the cache.
        Handle<Object> result = isolate()->factory()->undefined_value();
        int generation;
        for (generation = 0; generation < generations(); generation++) {
            Handle<CompilationCacheTable> table = GetTable(generation);
            result = table->LookupRegExp(source, flags);
            if (result->IsFixedArray())
                break;
        }
        if (result->IsFixedArray()) {
            Handle<FixedArray> data = Handle<FixedArray>::cast(result);
            if (generation != 0) {
                Put(source, flags, data);
            }
            isolate()->counters()->compilation_cache_hits()->Increment();
            return scope.CloseAndEscape(data);
        } else {
            isolate()->counters()->compilation_cache_misses()->Increment();
            return MaybeHandle<FixedArray>();
        }
    }

    void CompilationCacheRegExp::Put(Handle<String> source,
        JSRegExp::Flags flags,
        Handle<FixedArray> data)
    {
        HandleScope scope(isolate());
        Handle<CompilationCacheTable> table = GetFirstTable();
        SetFirstTable(
            CompilationCacheTable::PutRegExp(isolate(), table, source, flags, data));
    }

    void CompilationCache::Remove(Handle<SharedFunctionInfo> function_info)
    {
        if (!IsEnabled())
            return;

        eval_global_.Remove(function_info);
        eval_contextual_.Remove(function_info);
        script_.Remove(function_info);
    }

    MaybeHandle<SharedFunctionInfo> CompilationCache::LookupScript(
        Handle<String> source, MaybeHandle<Object> name, int line_offset,
        int column_offset, ScriptOriginOptions resource_options,
        Handle<Context> native_context, LanguageMode language_mode)
    {
        if (!IsEnabled())
            return MaybeHandle<SharedFunctionInfo>();

        return script_.Lookup(source, name, line_offset, column_offset,
            resource_options, native_context, language_mode);
    }

    InfoCellPair CompilationCache::LookupEval(Handle<String> source,
        Handle<SharedFunctionInfo> outer_info,
        Handle<Context> context,
        LanguageMode language_mode,
        int position)
    {
        InfoCellPair result;
        if (!IsEnabled())
            return result;

        const char* cache_type;

        if (context->IsNativeContext()) {
            result = eval_global_.Lookup(source, outer_info, context, language_mode,
                position);
            cache_type = "eval-global";

        } else {
            DCHECK_NE(position, kNoSourcePosition);
            Handle<Context> native_context(context->native_context(), isolate());
            result = eval_contextual_.Lookup(source, outer_info, native_context,
                language_mode, position);
            cache_type = "eval-contextual";
        }

        if (result.has_shared()) {
            LOG(isolate(), CompilationCacheEvent("hit", cache_type, result.shared()));
        }

        return result;
    }

    MaybeHandle<FixedArray> CompilationCache::LookupRegExp(Handle<String> source,
        JSRegExp::Flags flags)
    {
        if (!IsEnabled())
            return MaybeHandle<FixedArray>();

        return reg_exp_.Lookup(source, flags);
    }

    void CompilationCache::PutScript(Handle<String> source,
        Handle<Context> native_context,
        LanguageMode language_mode,
        Handle<SharedFunctionInfo> function_info)
    {
        if (!IsEnabled())
            return;
        LOG(isolate(), CompilationCacheEvent("put", "script", *function_info));

        script_.Put(source, native_context, language_mode, function_info);
    }

    void CompilationCache::PutEval(Handle<String> source,
        Handle<SharedFunctionInfo> outer_info,
        Handle<Context> context,
        Handle<SharedFunctionInfo> function_info,
        Handle<FeedbackCell> feedback_cell,
        int position)
    {
        if (!IsEnabled())
            return;

        const char* cache_type;
        HandleScope scope(isolate());
        if (context->IsNativeContext()) {
            eval_global_.Put(source, outer_info, function_info, context, feedback_cell,
                position);
            cache_type = "eval-global";
        } else {
            DCHECK_NE(position, kNoSourcePosition);
            Handle<Context> native_context(context->native_context(), isolate());
            eval_contextual_.Put(source, outer_info, function_info, native_context,
                feedback_cell, position);
            cache_type = "eval-contextual";
        }
        LOG(isolate(), CompilationCacheEvent("put", cache_type, *function_info));
    }

    void CompilationCache::PutRegExp(Handle<String> source,
        JSRegExp::Flags flags,
        Handle<FixedArray> data)
    {
        if (!IsEnabled())
            return;

        reg_exp_.Put(source, flags, data);
    }

    void CompilationCache::Clear()
    {
        for (int i = 0; i < kSubCacheCount; i++) {
            subcaches_[i]->Clear();
        }
    }

    void CompilationCache::Iterate(RootVisitor* v)
    {
        for (int i = 0; i < kSubCacheCount; i++) {
            subcaches_[i]->Iterate(v);
        }
    }

    void CompilationCache::MarkCompactPrologue()
    {
        for (int i = 0; i < kSubCacheCount; i++) {
            subcaches_[i]->Age();
        }
    }

    void CompilationCache::Enable()
    {
        enabled_ = true;
    }

    void CompilationCache::Disable()
    {
        enabled_ = false;
        Clear();
    }

} // namespace internal
} // namespace v8
